The present invention relates to a new and improved escalator combplate load and obstruction sensor capable of monitoring and indicating both horizontal and vertical force and load components.
Numerous load-based safety regulations control operating conditions for public escalators. Many of such regulations address load conditions at the escalator combplates, which serve as the entry and exit ways to the moving escalator steps. Such regulations may require, for example, that escalator power be interrupted in the event a force at greater than a particular level is applied to the escalator combplate in the (horizontal) direction of travel, or if a vertical force in the upward direction is applied to the combplate in excess of a specified minimum. Heretofore, safety systems intended to be responsive to such requirements have been of a mechanical nature. U.S. Pat. No. 5,611,417, for example, utilizes a bias trigger spring. Manual resetting of the device is required once triggered. The device set forth in U.S. Pat. No. 5,255,771 provides a pair of limit switches which are opened when the combplate is sufficiently displaced to overcome the force of override springs. In U.S. Pat. No. 5,307,918, the movement of the combplate resulting from the entrapment of an object between the steps and combplate creates activates a power interruption switch to stop further movement of the steps.
While the foregoing devices can provide for automatic shutdown of the escalator in the event of combplate displacement, they do not include a mechanism for the efficient preloading of the device to accommodate adjustments to the weight of the escalator combplate itself. Further, such devices have no facility for allowing the continuous monitoring of combplate loading.
It is accordingly a purpose of the present invention to provide a combplate load and obstruction sensor which is easily adjustable and can continuously monitor combplate load.
It is a further purpose of the present invention to provide a combplate load and obstruction sensor which is of both sensitive and rugged design.
It is still a further purpose of the present invention to provide a combplate load and obstruction sensor which can provide a plurality of control signals associated with both horizontal and vertical upward overloading conditions.
In accordance with the foregoing and other objects and purposes, an escalator combplate load and obstruction sensor apparatus constructed in accordance with the present invention comprises an electronic load cell transducer element mounted between the escalator combplate and the escalator frame. The load cell is preferably mounted to the combplate, and is engaged by a force-applying contact mounted to the escalator frame. The load cell may be mounted at an angle to both the horizontal and vertical. With the load cell at an angle to both the vertical and horizontal, both vertical and horizontal displacements of the combplate resulting from obstruction and lift forces are transmitted to and sensed by the load cell through the contact element. The combplate may be supported by a leveling device having a slightly compressive member such that downward displacements to the combplate occur as a result of personnel loading are applied to the load cell, allowing the continuous monitoring of use load as the load applied thereto varies.
The output of the load cell, which is preferably a voltage proportional to the load on the cell, is processed and compared to signals corresponding to set point force levels, such as the minimum vertical upward force or horizontal load for an alarm condition. Appropriate indicators and alarms may be activated when the set point loads are exceeded. With incorporation of an appropriate timer, unsafe or unstable operating conditions as may occur to prevent rapid user transit across the combplate can be recognized by monitoring the residence time of user load on the combplate.